Mineral nutrition plays a crucial role in the biochemical economy of green plants. As autotrophic organisms, plants synthesize all of the organic compounds they need for survival from inorganic mineral elements, most of which are derived from the soil.
Plant physiologists have determined that among the 90 or so chemical elements that occur in the earth's crust and atmosphere there are at least seventeen (17) elements that are essential for plant growth. An element is deemed to be essential if, in its absence, a plant fails to grow properly and complete its life cycle in a normal manner. The essential elements are listed in Table 1.
TABLE 1The Essential Elements and their Chemical SymbolsHydrogen-HCarbon-COxygen-ONitrogen-NPotassium-KCalcium-CaMagnesium-Mg Phosphorous-PSulfur-SChlorine-Cl Boron-BIron-FeManganese-MnZinc-ZnCopper-CuMolybdenum-Mo
TABLE 2Major ElementsHydrogen-HCarbon-COxygen-ONitrogen-NPotassium-KCalcium-CaMagnesium-MgPhosphorous-PSulfur-S
TABLE 3Minor ElementsChlorine -ClBoron- BIron-FeManganese-MnZinc-ZnCopper-CuMolybdenum-Mo
Biological Role of Essential Elements
The essential elements listed in Table 1, are arbitrarily classified as major (macro) or minor (micro), based on the relative amount of each element taken up and utilized by plants. According to most classification schemes, the elements, hydrogen through sulfur (see table 2) are regarded as major elements; the remaining seven (7) are grouped as minor elements (see table 3). Generally speaking, the major elements function as structural components of plant metabolites, besides acting as co-factors for enzymatic reactions. Minor elements primarily function as co-factors for enzymes.